Hashomer Hatzair came into being as a result of the merger of two groups, Hashomer ("The Guard") a Zionist scouting group, and Ze'irei Zion ("The Youth of Zion") which was an ideological circle that studied Zionism, socialism and Jewish history. Hashomer Hatzair is the oldest Zionist youth movement still in existence. Initially Marxist-Zionist, the movement was influenced by the ideas of Ber Borochov and Gustav Wyneken as well as Baden-Powell and the German Wandervogel movement. Hashomer Hatzair believed that the liberation of Jewish youth could be accomplished by aliyah (immigration; literally "ascent") to Palestine and living in kibbutzim. After the war the movement spread to Jewish communities throughout the world as a scouting movement.

Psychoanalysis was also an influence, partly through Siegfried Bernfeld; so was the philosopher Martin Buber. Otto Fenichel also supported Hashomer Hatzair's efforts to integrate Marxism with psychoanalysis. Hashomer Hatzair's educators sought to shape the image of the child from birth to maturity; some were aware of the work of the Soviet educator Anton Makarenko who also propounded collectivist education.[1]

Members of the movement settled in Mandatory Palestine as early as in 1919. In 1927, the four kibbutzim founded by Hashomer Hatzair banded together to form the Kibbutz Artzi federation. The movement also formed a political party which shared the name Hashomer Hartzair, advocating a binational solution in mandatory Palestine with equality between Arabs and Jews. That is why, when a small group of Zionist leaders met in New York in May 1942 in the Biltmore Hotel, Hashomer Hatzair representatives voted against the so-called Biltmore Program.

By 1939, Hashomer Hatzair had 70,000 members worldwide. The movement's membership base was in Eastern Europe. With the advent of World War II and the Holocaust, members of Hashomer Hatzair focused their attention on resistance against the Nazis. Mordechaj Anielewicz, the leader of Hashomer Hatzair's Warsaw branch, became head of the Jewish Fighting Organization and one of the leaders of the Warsaw Ghetto Uprising. Other members of the movement were involved in Jewish resistance and rescue in Hungary, Lithuania and Slovakia. The leaders of Hashomer Hatzair in Romania were arrested and executed for anti-fascist activities.

After the war, the movement was involved in organizing illegal immigration of Jewish refugees to Palestine. Members were also involved in the Haganah military movement as well as in the leadership of the Palmach.

Today, Hashomer Hatzair continues as a youth movement based in Israel, and operates internationally. In Europe, North and Latin America, as well as in Australia, Hashomer Hatzair organizes activities and camps (machanot) for the youth. Activities are still relatively ideological, but over time have been adapted to the needs of modern communities, vastly different from the context in which Hashomer Hatzair was created.

With the merger of the United Kibbutz Movement and Kibbutz Artzi, the likelihood of a merger between Hashomer Hatzair and UKM's youth movement, Habonim Dror, has increased and the two youth movements, once rivals, have increasingly co-operated in various countries where they co-exist. The movements even share an office in New York. However, the views of each movement on religion may be an obstacle to merger as Habonim Dror has a stronger identification with cultural Judaism as opposed to Hashomer Hatzair, which has been at times stridently secular and anti-religious — seeing itself as a leader of a legitimate expression of a secular stream of Judaism.

Once a huge movement inside the large Argentinian Jewish Community, Hashomer Hatzair Argentina suffered from decay common to all Zionist youth movements in Argentina during the last decades, as well as several military dictatorships in the country's history that directly or indirectly led to the closure of several of its kenim. Today the movement operates in Tzavta Centro Comunitario (Tzavta Community Center), in the neighborhood of Almagro, City of Buenos Aires. It is one of 9 Zionist Youth Movements in the city. It has around 120 members, running regular Saturday activities and secular Kabalat Shabat service, besides two machanot per year.

The movement in Australia is located in Melbourne and was established in 1953 as a break away from Habonim Dror. There was briefly a ken (branch) in Sydney during the 1960s, but it closed due to a lack of members. Many of the original bogrim (leaders) of Australian Hashomer Hatzair settled in kibbutz Nirim. Its building in Melbourne is known as Beit Anielewicz, located in the suburb of St Kilda East. It runs weekly meetings as well as bi-annual camps which take place in the Australian outback, during the summer and winter months. Hashomer Hatzair Australia is a member of the Australasian Zionist Youth Council (AZYC).

Currently there are close to one hundred members of 'Hashy' Australia. Meetings are held every Sunday from 2:30–4:30pm for Juniors and 5:30–7:30pm for Senior. During Year 10 (age: 15–16) chanichim undergo a 'hadracha' (leadership) course. This course is run by current bogrim in the movement and teaches the chanichim leadership skills which are used when they lead members of the Junior movement in Year 11. The current Year 11 madatzim (leaders) are from the group of Yad Mordechai.

Hashomer Hatzair Australia has a strong belief that chanichim should be active in the community, helping whenever they can. Members often go to rallies, actively pursue social justice locally and abroad, and run programs for disadvantaged children.

As with most of the kenim around the world, every year Hashy sends the chanichim who have just completed school on a 10-month Shnat program in Israel.

The Austrian Hashomer Hatzair traces its roots to the original Hashomer Hatzair founded in the Galicia region of the Austro-Hungarian Empire. The Hashomer were among the earliest members of the Österreichischer Pfadfinderbund in 1914. We also founded the first Ken which is located at Desider-Friedmannplatz 1b, 1010 Vienna. It holds around hundred members. The Ken meets every Saturday at 3:00, its peulots are usually from 3-5 and the evenings program is from 5-7. The Ken usually has four active kvutzots and one Bogrim kvutza. The Ken has two machanot each year in the winter and summer and a couple of tijulim, every second year the oldest kvutzot the bogrim and the oldest kvutza go to machane Israel in which they attend the Seminar Tzofi or Tzofinodet.

In Belgium, Hashomer Hatzaïr was established in 1920. Today, 300 hanihim come each Saturday to take part in folk dancing (rekudei'am), ludic activities (peoulot) and Shabbat celebrations (oneg shabbat). Four camps are organized throughout the year. The November, Winter and Easter camps usually take place in the Netherlands and the Summer camp in France. The shaliah is Tal Eitan and the shirfa madrihim is composed of the kvutzot of Revadim (1999) and Evron (2000), the two biggest kvoutzot. The Rashei Ken are Yoram Olesnicki and Livia Soro. Until 2005 there was a ken in Liege, but it closed because it was too small. Hashomer Hatzaïr in Belgium is part of the Brith which is composed of the five zionist youth groups of Belgium : Hashomer Hatzair, Hanoar Hatzioni, Habonim Dror, Bnei Hakiva and Jeunesse Juive Laïque.

In Brazil, the movement is informally called "Shomer" and has four branches: Rio de Janeiro (2), São Paulo and Florianópolis. Normally, the activities encompass weekly meetings as well as two summercamps (machané) per year, one of them being a national one. In Rio, where the tnuah is bigger, it embodies one of the left-wing Zionist institutions in the local Jewish community, playing a leading role in subjects like the peace process in the Middle East. The educational activities are also aimed at the challenges of Brazilian society, such as social and environmental issues. There are about 180 members in the national movement

In the United States and Canada camps last through the school summer vacation. The two summer camps in Liberty, New York, USA and Perth, Ontario, Canada are both called Camp Shomria or "Mosh". In addition, the movement runs activities in cities across the continent throughout the year promoting the peace process, socialist-Zionism, Hagshama Atzmit (self-actualization), social activism (tikkun olam), and withdrawal from the West Bank and Gaza.

Through seminars, camps (winter/summer), worldwide programs, and weekly activities wherein youth leads youth, Hashomer Hatzair aims to create a just world through socialism, equality, and the betterment of Israel and the world.

There are currently kenim in Toronto, northern New Jersey (Tenafly), central New Jersey (East Brunswick), New York City, Washington D.C., and Philadelphia. The United States is currently in the process of recreating kenim in Westchester, NY and Albany, NY.

The Chilean branch of Hashomer Hatzair was founded more than 60 years ago and it continues educating young Jewish Chileans with the values of social justice, fraternity, judaism and love for Israel. Currently there are 50-100 members aged 9–22 who meet every Saturday in the Ken located in Santiago. These are young chaverim that self organize and most of them do not belong to any Jewish collectivity or entity, thus most of them will have no link to anything Jewish if it wasn't for the tnua. For further info, visit the up-to-date website in Spanish.

In France, the youth movement spells Hachomer Hatzaïr with a "c". It was founded in Paris in Belleville area, in 1933, by Jews from Poland and Tunisia. The French branch now has about 500 members in two kenim, in Paris and Lyon. The khanikhim (children) (literally, "students") and Bogrim (organizers) (literally, "adults") meet weekly in groups and run 3 makhanot ("Resorts & Leisure") (literally, "camps") in November (or late October), around the end of December, and for 3 weeks in July. The French movement has 3 branches:[8] An educational branch, a political arm, and an "emsheh" branch.

Hashomer Hatzair has been re-established in 1989 in Budapest. Today it's one of the largest Zionist youth movements in Hungary. They have three camps every year and they have various programs for Jewish youngsters like bringing charity to Hungarian Holocaust Survivors or help cleaning out Jewish cemeteries in the countryside. Hashomer Hatzair has approximately 50 members nowadays in Budapest.

Today, the movement has around 80 kens all over Israel. In 2010, there were around 7,000 official members, the fourth largest youth movement in Israel by members.[9] The main actions of the movement is regular activities for youth ages 9–18, education for the tnua values and social actions.

Every year the movement has conference for the whole "Gub" ("Guf Boger", the members who guiding in the kens, ages 15–18) for discuss the yearly topic that related to the Israeli society, the kenim and the movement. At the end of the conference the members Formulates the results of the discussions for charta that represent the position of the tnua. Examples for topics: Zionism with peace, equality between genders, Socialism, Judaism in Hasomer Hatzair etc.

After the 1948 Arab-Israeli War, the Hashomer Hatzair Workers Party merged with other left wing parties to form Mapam which became the political party of both the youth movement and the Kibbutz Artzi federation. In Israel it was traditionally aligned with Mapam and later Meretz. It is not officially aligned with Meretz's successor party, Meretz-Yachad. After a recent merger of the Meretz-aligned Kibbutz Artzi Federation with the Labour Party's United Kibbutz Movement, Hashomer Hatzair is officially not aligned with either party though, by tradition, it is close in outlook to Meretz-Yachad.

The Mexican branch of Hashomer Hatzair was established in 1940. Since 1983, its "ken" (Hebrew for "nest", i.e., its headquarters), named after Mordechai Anielewicz, is currently located in the Polanco neighbourhood, western part of Mexico City.

Hashomer Hatzair Mexico was founded by Avner Aliphas, a Hebrew professor at the Yiddish school of Mexico and later founder of the "Tarbut" Jewish day school in 1942. Aliphas was born in Kolno, Poland, in 1911, and made aliyah (immigrated to Eretz Israel) in 1936 to join Kibbutz Negba, and in 1938 he helped establish Kibbutz Hanita. In 1939 he returned to Kolno after his mother died and luckily got out before the Nazi invasion to attend a Zionist conference in Paris. When the war broke out and could not go back to Israel, he traveled to Mexico where he became active in the Zionist movement.

In 1940, supported by the Zionist Organization in Mexico, Aliphas founded Hashomer Hatzair in Mexico, thus giving an option for young people who had been educated towards Zionism at home. This was the first Jewish youth movement that existed in the country; its first Ken was in Tacuba 15, in the city center.

During the next decades, Hashomer Hatzair was one of the places for secular socialization for the Jewish community. As of the present day, the Mexican branch of Hashomer Hatzair comprises approximately fifty members who regularly attend cultural, educational and sporting events as a group.

Hashomer Hatzair has existed in Uruguay since 1946. In its early stages, there were two different kinim but now there is only one in the centre of the city, consisting of two kvutzot of younger children (ages 6 to 7 and 8 to 10) and another two of older kids (11 to 13 and 14 to 16). The ken is called Ken Negba and is in the capital city of Montevideo.

Hashomer Hatzair was active in the Netherlands since the '50s. Until somewhere in the '70s there were kenim in Rotterdam and Amsterdam. After that there is no record of shomeric activity in the Netherlands. However, there is a ken in Maastricht which has been active since around the year 2000. The ken has two kvutzot of older and younger kids (9-12 and 5-8). Ken Maastricht has been part of the World Movement since 2011.

In Switzerland, Ken Yitzhak Rabin in Zürich consists of some 100 hanihim, meeting on Shabbat afternoon and for two or three camps (annually in autumn and winter, bi-annually in summer), next to the Bogrim's bi-annual trips to Israel or Poland. Special events are held for Pessach, Chanuka and the Yitzhak Rabin memorial. The Ken was founded in 1935 and joined World Hashomer in 1938. During the 2nd world war, there were five major Kenim (Zurich, Basel, Berne, Biel, Geneva) plus activities in a few smaller cities and in the refugee centers. Swiss Shomer members having made aliya can be encountered e.g. in Lehavot Habashan and Magen. As of 2009[update] the Shomer was the largest Jewish youth movement in Switzerland.

Hashomer Hatzair in Venezuela was founded in 1954 in Caracas, coming through Tamar Campo, an immigrant girl from Cuba, who began doing educational activities in September 1954 for young Jews of Venezuela, during the Rosh Hashana festivities . The name is Ken Najshon , inspired like the prince of the tribe of Judah, who led the Jewish people out of Egypt across the waters opened by Moses .

Today the Ken Najshon continues educating young's in the Jewish community of Venezuela, every Saturday at the Hebraica club by peulot where they teach about Zionism, socialism and humanistic Judaism and are taught values of equality, social justice and brotherhood through non-formal education .

Around the world, Hashomer Hatzair members have founded a life movement to pick up where the youth movement leaves off. Groups have been organized in Israel by Israelis and non-Israelis, and others were formed in their countries of origin (such as in Canada, the United States, Switzerland and Hungary).

The Life Movement in the United States and Canada has created three urban communes, one in New York and two in Toronto where members are experimenting with the Israeli model of communot in their home societies. In addition, a new winter trip to Israel for Bogrim called Mifgash takes place yearly.